Machine tool

ABSTRACT

The machine tool comprises a machine stand (10) with a vertically movable vertical carrier (12) carrying a spindle head (SK1) for treatment of a workpiece. To exchange the spindle head (SK1) against a new spindle head (SK2), an exchange unit (15) is provided, comprising an exchange arm (16) pivotable by 90° about a vertical axis (37). Two holding couplings (17,18) are mounted above each other on the exchange arm (16), each adapted to carry a spindle head (SK1,SK2). A delivery means (21), gripping the spindle heads from above, is used to supply the spindle heads for transfer to the exchange unit (15). The exchange unit (15) grips the spindle heads from the side. By pivoting the exchange arm (16) over 90°, the spindle head is pivoted to a position in front of the machine stand (10) and thus can be taken over by the vertical carrier (12).

BACKGROUND OF THE INVENTION

The present invention relates to a machine tool of the type comprising amachine stand and a changeover device for the exchanging of spindleheads fastened to a vertical carrier of the machine stand to performtreatment of a workpiece.

From DE 39 18 902 A1, a machine tool is known wherein the spindle headfastened to a vertical carrier can be exchanged. For this purpose, achangeover device is mounted to the machine stand, comprising twoexchange arms pivotable by respectively 180°. Each exchange arm can gripthe upper end of a spindle head delivered from a magazine and, through apivoting movement of 180°, position the spindle head adjacent thevertical carrier, so that the spindle head can be transferred to thevertical carrier to be locked thereon. The spindle head suspended on theexchange arm can be turned by 90° relative to the exchange arm in such amanner that the tools projecting from the exchange arm, which in theiroperating position are oriented in the forward direction from to themachine stand, upon transfer to the spindle head magazine will projectfrom the machine stand in a lateral direction. To allow a quick exchangeof the spindle heads, two exchange arms are required, one exchange armremoving the spindle head from the vertical carrier while the otherexchange arm supplies a new spindle head to the vertical carrier. Suchan arrangement requires a high technical expenditure for the exchangearms. The spindle head magazine must extend to both sides of the machinestand and necessitates a complex transport mechanism.

Further, in a machine tool known from EP 0 204 151 B1, the spindle headsare suspended on a head exchange unit arranged on the machine stand forrotation about a vertical axis. The spindle heads are seized from aboveand pivoted to a position above the moving path of the vertical carrierwhich then will take over the spindle heads. This construction makes itnecessary to provide a head exchange unit with a large turning radius onthe machine stand, and the outwardly projecting spindle heads and toolsrequire considerable space.

In a machine tool known from DE 92 02 245 U1, the machine stand isarranged next to a transfer station. The machine stand supports avertical carrier which is movable in a vertical direction and isprovided with an exchange arm pivotable about a horizontal axis. On thetransfer station, two transfer sites are arranged above each other, eachof them adapted to receive one spindle head. The exchange arm islaterally pivoted towards one of the two spindle heads and then pullsthe spindle head horizontally to the vertical carrier. For exchange ofthe spindle heads, not only a vertical movement of the vertical carrierbut also several reciprocating movements of the exchange arm must beperformed. Additionally, it is required that the spindle heads at thetransfer station and on the vertical carrier be guided in vertical guidebars, while a wide gap must be bridged for transfer of the spindleheads.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a machine tool wherein theexchange unit requires little space and is adapted to perform anexchange of the spindle heads by a simple moving sequence and within ashort time.

According to the instant invention, the above object is solved by thefeatures indicated in claim 1.

In the machine tool according to the invention, the exchange armcomprises two holding couplings arranged above each other and providedfor respectively one spindle head, and the vertical carrier is movableto the transfer height of each of the holding couplings. The exchangearm can be pivoted about a vertical axis into a transfer position inwhich the holding coupling of the exchange arm is pivoted to a spindlehead placed on the vertical carrier. The same exchange arm has the newspindle head attached thereon, which will be positioned below or abovethe spindle head to be replaced. During the transfer of the old spindlehead to the exchange arm, the new spindle head still remains connectedto the exchange arm. Once the vertical carrier has transferred the oldspindle head to the exchange arm, the vertical carrier is movedvertically into alignment with the new spindle head which then will betransferred to the vertical carrier. In this manner, only one pivotingmovement of the exchange arm into the transfer position, followed by areverse pivoting movement, is required for performing a completeexchange of spindles.

Preferably, the exchange unit is arranged separately from the machinestand, with the machine stand being movable in the forward directionrelative to the exchange unit. In the context of the instantdescription, the forward direction is the direction of the machine standadvance axis (Z-axis) in which the tools of the spindle head on thevertical carrier are oriented. It is generally possible to put themachine stand to a standstill and to move the exchange unit. Since themachine stand is usually movable in the direction of the Z-axis anyway,the exchange unit is preferably fixed. The movement in the Z-directionis suitable to completely release a spindle head from its engagementwith the vertical carrier after transfer of the spindle head to theexchange unit. When the vertical carrier has then been moved to thetransfer position for the new spindle head, the machine stand isadvanced so that the vertical carrier can reliably seize the new spindlehead. This advance and return movement of the machine stand is alwaysperformed only over a very short travelling distance which is requiredto remove the vertical carrier from the spindle head that transferredthe exchange unit.

Preferably, the exchange arm is pivotable by only 90°, the deliverymeans passing the spindle head over to the exchange arm with the toolsfacing laterally away from the machine stand. This means that theexchange arm performs exclusively a pivoting movement whilesimultaneously pivoting the spindle head suspended thereon by 90°. Thefront side of the spindle head, i.e. the side having the toolsprojecting therefrom, will then be laterally facing away from themachine stand in the direction of the horizontal x-axis. In thisorientation, the spindle heads can be removed from the machine stand andbe transferred into a spindle head magazine. This configuration offersthe advantage that the front sides of the spindle heads and the toolsprojecting therefrom can be easily checked and visually observed sincethey are accessible to the maintenance staff from one side of themachine tool. Further, on this side, an automatically operated toolmonitoring device can be arranged. The whole movement and storage of thespindle heads takes place in the above orientation, with the toolsoriented in the direction of the X-axis of the machine stand.

Preferably, the holding couplings of the exchange arm are provided toengage holding portions arranged in a side wall of each spindle head.This allows for a considerably less complex design because the exchangearm can be shaped as a plate and does not need projecting portionsgripping the spindle head from above. As a result, the exchange unit canbe given particularly compact and space-saving dimensions.

On the other hand, the delivery means, provided to deliver the spindleheads to the exchange unit and again remove them from the exchange unit,can have a holding coupling for engagement with holding portions formedon the upper side of the spindle head. Thus, while the exchange unitengages holding portions arranged laterally on the spindle head, thedelivery means engages holding portions arranged on the upper side ofthe spindle head. In this manner, the coupling systems of the exchangeunit and the delivery means are functionally and spatially separatedfrom each other and thus will neither influence nor disturb each other.

According to a preferred embodiment of the invention, the delivery meanscomprises a lift which can be moved to the transfer height of each ofthe two holding couplings of the exchange unit. This lift supports ahorizontal carrier arranged for linear movement in parallel to the frontplane of the machine stand, i.e. in the X-direction. In this manner, thedelivery means can insert the spindle head by a linear movement into theholding coupling of the exchange unit arranged in its waiting position.This movement can be performed quickly and with low noise.

According to a further embodiment of the invention, the carrier isarranged on a carriage which can be moved in parallel to the forwarddirection of the machine stand, i.e. in the direction of the Z-axis, forservicing a shelf magazine. This carriage makes it possible for thedelivery means to service both the shelf magazine and the exchange unit.The lift is used for movement not only to the respective transfer heighton the exchange unit but also to the height of the compartment of theshelf magazine which is to be serviced. The horizontal carrier is usedfor the movement into the compartments of the shelf magazine and for theadvancing of the spindle heads to the exchange arm in its waitingposition.

A preferred embodiment of the invention will be explained in greaterdetail hereunder with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a plan view of the machine tool,

FIG. 2 shows a front view from the direction of the arrow II in FIG. 1,

FIG. 3 shows a side view from the direction of the arrow III in FIG. 1;and

FIG. 4 shows a perspective view illustrating an exchange process forexchanging an old spindle head against a new spindle head.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The machine tool comprises a machine stand 10 which, by means of asliding carriage (not shown), is movable in the direction of the X-axison the machine base 11. Machine stand 10 is also movable in the frontdirection, i.e. in the direction of the Z-axis. The movability ofmachine stand 10 in the direction of the X-axis is not absolutelynecessary. On the front side of machine stand 10, a vertical carrier 12is arranged for movement in a vertical direction (in the direction ofthe Y-axis). Attached on vertical carrier 12 is the spindle head SKwhich on its front side is provided with tools 13 for treatment of aworkpiece (not shown). These tools 13 are e.g. drilling or millingdevices which are rotatably driven. The tools 13 can be exchanged onspindle head SK. Spindle head SK contains a holding fixture and a drivegear for the rotatory drive of tools 13. The tools are driven from theinterior of machine stand 10 via vertical carrier 12. Vertical carrier12 is provided with a holding means arranged to grip the spindle head SKand hold it in a defined position on vertical carrier 12. Verticalcarrier 12 can be displaced on machine stand 10 along vertical guiderails 14 illustrated in FIG. 2.

The exchange unit 15 is arranged in a fixed position on machine base 11on the one end of the moving path of machine stand 10 in theX-direction. Exchange unit 15 comprises an exchange arm 16 which ispivotable by 90° about a vertical axis 37. Exchange arm 16 can bepivoted into the waiting position 16a wherein it extends in parallel tovertical carrier 12, and into a transfer position 16b wherein it extendsat a right angle to vertical carrier 12, i.e. in the direction Z-axis.Two holding couplings 17,18 are arranged above each other on exchangearm 16. Each of the holding couplings 17,18 comprises a block from whichclamping portions 19 are simultaneously extendable upwardly anddownwardly. Each clamping portion 19 comprises a prism-shaped centeringelement adapted to engage a complementary holding portion 20 of spindlehead SK to hold and lock the spindle head SK in its exact position onholding coupling 17. The holding portions 20 are horizontal barsarranged on a side wall of spindle head SK and formed to have thecoupling means 17 or 18 fittingly engage therebetween in the retractedstate of the clamping portions 19. When the clamping portions 19 areextended, they enter the holding portions 20 and thus fixeldly hold thespindle head SK on the coupling means 17 and 18, respectively.

The transport of the spindle heads SK to and from the holding couplings17,18 is performed by the delivery means 21. Delivery means 21 comprisesa lift 22 vertically displaceable on a carriage 23. Lift 22 has ahorizontal carrier 24 mounted thereon which is movable in the directionof the X-axis and in the illustrated embodiment is provided as atelescopic slide with a plurality of telescopic elements. Horizontalcarrier 24 engages, by means of a holding coupling (not shown), holdingmembers 25 provided on the upper side of spindle head SK. Lift 22 isused for moving the horizontal carrier 24 to the respective transferheight of holding couplings 17 or 18. Then, horizontal carrier 24 isextended, and spindle head SK is moved along the holding couplings 17,18until reaching the transfer position. In the transfer position, theclamping portions 19 are extended out of the holding couplings 17 and18, respectively to engage holding portions 20. Subsequently, theholding couplings of the horizontal carrier 24 are released so that thehorizontal carrier 24 can be returned without the spindle head.

The shelf magazine 35 for depositing the spindle heads is arrangedlaterally of machine stand 10 in the Z-direction. On the side of shelfmagazine 35 facing away from machine stand 10, guide rails 26 arearranged to have the carriage 23 running thereon; thus carriage 23 willmove along the outer side of shelf magazine 35. An additional guide railis arranged on the upper edge of shelf magazine 35. Shelf magazine 35comprises a large number of compartments wherein the spindle heads SKcan be suspended. Each compartment includes a holding means 27 (FIG. 3)which has the holding portions 20 of a deposited spindle head SKgripping therearound and which holds the spindle head in a mannersimilar to the holding couplings 17,18. The holding means 27 are eachfastened to a side wall of shelf magazine 35. When lift 22 of carriage23 moves towards a shelf compartment, the horizontal carrier 24 can beentered into the shelf compartment to engage the holding members 25 onthe upper side of spindle head SK and thus take the spindle head SK outof the shelf compartment. Then, spindle head SK will be retracted intocarriage 23 and moved into the transfer station 28 arranged at the endof shelf magazine 35. Arranged within transfer station 28 is theexchange unit 15 whose exchange arm 16 can take over the spindle headSK.

FIG. 4 illustrates the condition wherein the vertical carrier 12 ofmachine stand 10 carries a spindle head SK1--hereunder briefly referredto as an "old spindle head"--which is to be exchanged for a "new spindlehead" SK2. Spindle head SK2 has been taken out of the shelf magazine 35by delivery means 21. Subsequently, carriage 23 has been moved totransfer station 28. When lift 22 has been moved to the transfer heightof the lower holding coupling 18, horizontal carrier 24 has beenextended, with the holding portions 20 of spindle head SK2 gripping fromabove and below--the holding coupling 18 of the exchange arm 16 whichhas been pivoted into its transfer position. Then, holding coupling 18is actuated to extend the clamping portions 19 and have them engage theholding portions 20. Once spindle head SK2, arranged in its transferposition, has been taken over by exchange arm 16, it is released fromthe horizontal carrier 24 which then is retracted into lift 22. Now,exchange arm 16 is pivoted by 90° about the vertical axis 37. This isperformed by a drive motor 29, arranged on the upper side of exchangearm 16, which has a pinion engaging a ring gear 30 seated on the upperend of the stationary and non-rotating axis 37. The pivoting movement islimited, by two stoppers 31, to exactly 90°. At the end of the pivotingmovement, spindle head SK2 is arranged in parallel to carrier 12 infront of machine stand 10. The moving range of vertical carrier 12 onmachine stand 10 has such a vertical dimension that both spindle headsSK1 and SK2 can be positioned above each other in front of machine stand10.

While exchange arm 16a is arranged in the transfer position 16b (FIG.1), it holds the new spindle head SK2 fixed in position, and in thisposition, its other holding coupling 17 is already arranged between theholding portions 20 of the other spindle head SK1. Now, by extending theclamping portions 19 from the holding coupling 17, also the old spindlehead SK1 is taken over by exchange arm 16 and shortly afterwards isreleased from vertical carrier 12. In this situation, both spindle headsSK1;SK2 are carried by exchange arm 16.

To release the vertical carrier 12 from its engagement with the oldspindle head SKI and render the vertical carrier 12 free of spindle headSK1, machine stand 10 is moved back a short distance along the Z-axis.Then, vertical carrier 12 is lowered to the position of lower spindlehead SK2, and machine stand 10 is again advanced a short distance sothat the engagement members of vertical carrier 12 can enter thecorresponding engagement portions 32 on the rear side of spindle headSK2 and the drive connection between vertical carrier 12 and spindlehead SK2 is established. Once spindle head SK2 has been taken over byvertical carrier 12, spindle head SK2 is released from holding coupling18.

Subsequently, exchange arm 16 together with the old spindle head SK1 ispivoted back into the waiting position 16a shown in FIG. 4. Lift 22 israised to the upper takeover position, and horizontal carrier 24 isextended so as to seize spindle head SK1 by its upper holding members 25and remove it from holding coupling 17 in the direction of the X-axis.In the process, the tools 13 of spindle head SK1 project laterally frommachine stand in the direction of the X-axis. Already in the transferstation 28, the tools can be inspected and exchanged. At the transferstation 28, carriage 21 transports the spindle head SK2 into shelfmagazine 35, with the movement of spindle head SK2 into magazine 35being effected by extending the horizontal carrier 24.

Although a preferred embodiment of the invention has been specificallyillustrated and described herein, it is to be understood that minorvariations may be made in the apparatus without departing from thespirit and scope of the invention, as defined the appended claims.

We claim:
 1. A machine tool comprising a machine stand (10) supporting avertically movable vertical carrier (12) for attachment of a spindlehead (SK), an exchange unit (15) including an exchange arm (16)pivotable about a vertical axis (37) and provided with a holdingcoupling (17, 18) for engagement with a spindle head (SK) delivered bydelivery means (21) and for transfer of the spindle head to the verticalcarrier (12), the exchange arm (16) includes two holding couplings (17,18) arranged above each other and provided for coupling to respectivespindle heads (SK, SK1, SK2), means for moving the vertical carrier (12)to the transfer height of each of the holding couplings (17, 18), theholding couplings (17, 18) of the exchange arm (16) are provided forengaging holding portions (20) arranged on a side wall of each spindlehead (SK) each spindle head (SK) having holding members (32) at abackside of each of said spindle heads (SK), and said exchange arm (16)being pivotable to a transfer position (16b) in which a spindle head(SK) fixed to a holding coupling (17, 18) of said exchange arm (16) ispositionable in front of said vertical carrier (12) in such a mannerthat engagement members of the vertical carrier (12) engage said holdingmembers (32) at the backside of said spindle head (SK).
 2. The machinetool according to claim 1, characterized in that the exchange unit (21)is arranged separately from the machine stand (10) and the machine stand(10) is movable in the forward direction (Z-axis) relative to theexchange unit (21).
 3. The machine tool according to claim 1,characterized in that the exchange arm (16) is pivotable by 90° and thedelivery means (21) passes the spindle head (SK) over to the exchangearm (16) with the tools (13) facing laterally away from the machinestand (10).
 4. The machine tool according to claim 1, characterized inthat the holding couplings (17,18) of the exchange arm (16) are providedto engage holding portions (20) arranged in a side wall of each spindlehead (SK).
 5. The machine tool according to any one of claims 1 to 4,characterized in that the delivery means (21) is provided with a holdingcoupling for engagement with holding portions (25) arranged on the upperside of the spindle head (SK).
 6. The machine tool according to claim 1,characterized in that the exchange unit (15) is stationary, the deliverymeans (21) comprises a lift (22) which can be moved to the transferheight of each of the two holding couplings (17,18) of the exchange unit(15), and the lift (22) supports a horizontal carrier (24) which can bemoved in parallel to the front plane of the machine stand (10) (in thedirection of the X-axis).
 7. The machine tool according to claim 6,characterized in that the lift (22) is arranged on a carriage (23) whichcan be moved in parallel to the forward direction of the machine stand(10) (in the direction of the Z-axis) for servicing a shelf magazine(35).
 8. The machine tool according to claim 7, characterized in thatthe shelf magazine (35) includes storage compartments provided withholding means (27) engaging the lateral holding portions (20) of thespindle heads (SK).
 9. The machine tool according to claim 4,characterized in that the holding couplings (17,18) of the exchange arm(16) comprise upwardly and downwardly extendable clamping portions (19)for centered engagement into the holding portions (20) of the spindlehead (SK).
 10. The machine tool according to claim 2, characterized inthat the exchange arm (16) is pivotable by 90° and the delivery means(21) passes the spindle head (SK) over to the exchange arm (16) with thetools (13) facing laterally away from the machine stand (10).